1. Field of the Invention
The present invention relates to the process for purification of crude metal chlorides, particularly aluminum chloride. More particularly, the subject of the present invention provides for a process for improving rates and yield in the purification of aluminum chloride through the additional elemental sulfur or equivalent sulfur containing compounds and powdered aluminum or equivalent aluminum containing compounds during the purification of the aluminum chloride under agitation and the subsequent removal of trace sulfur through granular aluminum reaction prior to the collection of the pure solid aluminum chloride.
2. General Background
The aluminum industry is illustrative of a situation wherein high grade bauxite or other aluminum containing ores represent limited reserves. However, kaolinitic clay provided a virtually inexhaustible reserve for the aluminum industry. Ore chlorination processes offer what is the most promising economic means for removal and recovery of the valuable aluminum chlorides; however, for example, major obstacles have been the low rates of chlorination, the low yield of aluminum chloride, and the difficulty of obtaining aluminum chloride in sufficient purity for use in various applications.
The overall process of the present invention relates to the purification of aluminum chloride which result primarily from the carbo-chlorination of aluminum containing ores to make the crude aluminum chloride itself. The chlorination of metallic ores in the presence of the sulfur and/or one or more functionally equivalent sulfur containing compounds is known in the art, however, the purification of the resulting crude aluminum chloride through the addition of sulfur and/or equivalent sulfur containing compounds for high yield of pure aluminum chloride and aluminum powder and/or aluminum containing compounds for high quality pure aluminum chloride and the subsequent sublimation of the pure aluminum chloride, lends itself to an entire novel process not found in the art.
Processes for the conversion of the various ores into metallic halides and the subsequent purification of the resulting metallic halide (particularly aluminum chloride) are fairly well known in the art. Also, the utilization of sulfur and/or sulfur containing compounds as reducing agents during the carbo chlorination phase of the production of aluminum chloride has been documented in the literature. For example, U.S. Pat. Nos. 1,858,272; 1,422,568; and 1,405,115 all disclose processes for chlorinating clay and alumina utilizing mixtures or chlorine and sulfur or sulfur chlorides. Also, U.S. Pat. Nos. 1,581,272 and 1,325,203 describe the chlorination of aluminum metals using chlorine and other compounds. U.S. Pat. No. 4,082,833 also teaches the process of clay chlorination, yet stopping far short of the subsequent process for purification of the aluminum chloride resulting therefrom.
In that regard, U.S. Pat. No. 3,938,969 and U.S. Pat. No. 4,035,169 both assigned to Toth Aluminum Corporation teach a method for the recovery of aluminum chloride and the subsequent purification thereof.
U.S. Pat. No. 1,645,143 and Russian Pat. No. 684,000 employ the use of aluminum metal being injected into an aluminum chloride melt, U.S. Pat. No. 1,645,143 in particular illustrating the resulting displacement of the iron from the metal chloride and the subsequent sublimation of the pure aluminum chloride therefrom. However, particularly in U.S. Pat. No. 1,645,143 patent, the aluminum chloride which will result from the sublimation, which is a very slow process, is indeed not as pure as the patent would indicate, and thus still resulting in substantial impure and low yield aluminum chloride. Therefore, there is a significant need in the art for a process which would both yield a high grade aluminum chloride with less than 0.05% iron chloride and a high yield aluminum chloride from the crude aluminum chloride being processed. Such is the case of the present invention.